Guest blog from Sir John Harman, Senior Independent Director at the Energy Saving Trust

Well, I asked for it. The Home Action Plan, that is. I knew that a house like ours – solid stone walls, almost no attic void to speak of – would be a bit of a challenge but the assessor who came was still able to make a good number of suggestions for improving its energy performance.

One of them was to apply internal wall insulation. So, when it came to redecorating the guest bedroom, that's what I did.

Now, you can't go down to your local B&Q and buy a couple of rolls of this stuff. They either try to sell you plastic wallpaper of the sort that I had thought went out in the seventies, or insulation board. I found one supplier, via the internet, a product called SempaTap. It comes via courier; you order the wall lining itself, and appropriate amounts of glue, edging and filler. The bedroom has two external walls and the material cost me about £200 all in.

Applying this material is within the capability of a reasonably competent amateur, a bit like very, very difficult wallpaper. If you got your professional decorator to do it, I doubt he would find the job any easier. The stuff is heavy, expanded latex by the look of it, and about 1cm thick, so it needs serious glue. The glue was the worst bit, really. It is probably an epoxy resin of some sort, and if you have ever handled that in large quantity you will know it does stick to everything. You spread this stuff on the wall and then placing the material isn't too difficult – but you can't slide it around like you can with wallpaper paste. And cutting round obstacles and edges takes some patience and accuracy.

But when its up, it looks fine. The surface layer can just be painted, and you can see that the result looks like a normal finish. Unless you are very lucky, and have exactly flat, plumb surfaces to work with (and if you live in a house which needs this stuff, that will never be the case), there will be no such thing as a clean butt joint between rolls, and you make good the gaps with a special filler. You could then apply lining paper to get a perfect finish but I didn't and the result is satisfactory.

So it works, though I would hardly describe it as close to market; you need to really want this stuff to get it. Was it worth it? Well, when winter comes we'll know. I'll get our guests to blog in and tell us. Below is a photo of the finished room.

Bedroom